Hybridization is limited between two lineages of freeze-resistant Trichinella during coinfection in a mouse model

Hybridization and introgression of the mitochondrial genome between the two species Anisakis pegreffii and A. simplex (s.s.) using a wide genotyping approach: evolutionary and ecological implications

Anisakis pegreffii and A. simplex (s.s.) are the two zoonotic anisakids infecting cetaceans as well as pelagic/demersal fish and squids. In European waters, A. pegreffii prevails in the Mediterranean Sea, while A. simplex (s.s.) in the NE Atlantic Ocean. Abiotic conditions likely play a significant role in shaping their geographical distribution. The Iberian Atlantic and Alboran Sea waters are sympatric areas of the two species. A total of 429 adults and L3 stage from both sympatric and allopatric areas were studied by a wide nuclear genotyping approach (including newly and previously found diagnostic single nucleotide polymorphisms (SNPs) at nuclear DNA (nDNA) and microsatellite DNA loci) and sequenced at mitochondrial DNA (mtDNA) cox2. Admixture between the two species was detected in the sympatric areas studied by STRUCTURE Bayesian analysis; NEWHYBRIDS revealed different categories of hybridization between the two species, representing approximately 5%. A tendency for F1 female hybrids to interbreed with the parental species at the geographical distribution limits of both species was observed. This finding suggests that hybridization occurs when the two parental species significantly differ in abundance. Mitochondrial introgression of A. simplex (s.s.) in A. pegreffii from Mediterranean waters was also detected, likely as a result of past and/or paleo-introgression events. The high level of genetic differentiation between the two species and their backcrosses indicates that, despite current hybridization, reproductive isolation which maintains evolutionary boundaries between the two species, exists. Possible causes of hybridization phenomena are attempted, as well as their evolutionary and ecological implications, also considering a sea warming scenario in European waters.

An Update in Knowledge of Pigs as the Source of Zoonotic Pathogens

The available data indicate that the human world population will constantly grow in the subsequent decades. This constant increase in the number of people on the Earth will lead to growth in food demand, especially in food of high nutritional value. Therefore, it is expected that the world livestock population will also increase. Such a phenomenon enhances the risk of transmitting pathogens to humans. As pig production is one of the most significant branches of the world's livestock production, zoonoses of porcine origins seem to be of particular importance. Therefore, in this review, we aim to introduce the latest data concerning, among other things, epidemiology and available preventive measures to control the most significant porcine zoonoses of viral, bacterial, and parasitic origin.

Infection, genetics, and evolution of Trichinella: Historical insights and applications to molecular epidemiology

Genetic variation in pathogen populations provides the means to answer questions in disease ecology and transmission, illuminating interactions between genetic traits, environmental exposures, and disease. Such studies elucidate the phylogeny, evolution, transmission and pathogenesis of viruses, bacteria and parasites. Here, we review how such studies have fostered understanding of the biology and epidemiology of zoonotic nematode parasites in the genus Trichinella spp., which impose considerable economic and health burdens by infecting wildlife, livestock, and people. To use such data to define ongoing chains of local transmission and source traceback, researchers first must understand the extent and distribution of genetic variation resident in regional parasite populations. Thus, genetic variability illuminates a population's past as well as its present. Here we review how such data have helped define population dynamics of Trichinella spp. in wild and domesticated hosts, creating opportunities to harness genetic variation in the quest to prevent, track, and contain future outbreaks.

Trichinella species and genotypes

Trichinella spiralis has historically been deemed "the pig parasite" owing to its initial classification within a monospecific genus. However, in recent years, the genus has expanded to include 10 distinct species and at least 3 different genotypes whose taxonomic status remains unstipulated. In contrast to T. spiralis, however, most of these sylvatic species and genotypes do not infect pigs well. Inasmuch as morphological characters cannot be used to define species within this genus, earlier classifications were based upon host and geographical ranges, biological characters, and the presence or absence of a collagen capsule that surrounds the muscle stage larvae. Later, isoenzymes, DNA gel fragmentation patterns and DNA probes were used to help in identification and classification. Today, amidst the "-omics" revolution, new molecular and biochemical-based methodologies have improved detection, differentiation and characterization at all levels including worm populations. These efforts have discernably expanded immunological, epidemiological, and genetic studies resulting in better hypotheses on the evolution of the genus, and on global events, transmission cycles, host associations, and biogeographical histories that contributed to its cosmopolitan distribution. Reviews of this sort are best begun with a background on the genus; however, efforts will divert to the most recent knowledge available on the taxonomy, phylogeny, epidemiology and biochemistry that define this genus in the 21st century.

Intraspecific genetic variation in Trichinella spiralis and Trichinella britovi populations circulating in different geographical regions of Poland

Trichinella spiralis and Trichinella britovi are species of nematodes which are responsible for the majority of Trichinella infections in the world and the most prevalent in Poland. The most abundant species – T. spiralis, is considered to be more genetically homogeneous in Europe than T. britovi. The aim of the present study was to determine the genetic variability in T. spiralis and T. britovi populations based on nuclear 5S rDNA intergenic spacer region (5S rDNA) and cytochrome c oxidase 1 (COX1) gene sequences. For the study, 55 isolates of T. spiralis and 50 isolates of T. britovi isolated from wild boars, pigs, brown rat and a red fox were analyzed. Based on the analysis of both genes, the genetic variability within populations of T. spiralis and T. britovi differed. In T. spiralis, two single nucleotide polymorphisms (SNPs) were observed in the 612 bp 5S rDNA gene fragment, and one SNP was detected in the 700 bp COX1 gene fragment. In T. britovi, 17 single nucleotide variations (SNVs) were detected in the 5S rDNA gene fragment (among them 16 SNPs), while COX1 sequence analysis revealed the occurrence of 20 SNVs between the sequences tested (among them 19 SNPs).

For the majority of T. spiralis isolates the investigated larvae presented uniform haplotypes. In contrast, most of the isolates of T. britovi consisted of larvae of different haplotypes. Geographical analysis showed that each region exhibited different haplotype composition and richness. Warmińsko-Mazurskie and Zachodniopomorskie regions were the richest in haplotypes (15 and 16 haplotypes, respectively). We used heatmaps showing a characteristic pattern for each region graphically. This may allow to differentiate regions based on the occurrence of particular haplotypes. Furthermore, a PCA analysis on the SNP level yielded biplots that show that certain haplotypes/genotypes are associated with (clusters of) regions.

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The genetic variability within the Polish T. britovi population is high.

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5S rDNA and COX1 variability in T. spiralis is low compared to T. britovi.

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T. britovi variability may correlate to geographical origin.

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Heatmap and PCA analysis could be helpful analytical tool for epidemiological investigations.

Trichinella Nativa Outbreak With Rare Thrombotic Complications Associated With Meat From a Black Bear Hunted in Northern Ontario

Background

Although trichinellosis is known to cause thrombotic disease, serious thrombotic events are rare and have not been previously associated with Trichinella nativa infection.

Methods

Patient interviews and medical chart reviews were conducted on 10 men who became ill following consumption of a common source of black bear meat. Trichinella serology on patient sera as well as polymerase chain reaction (PCR) and larval identification of the meat samples was conducted.

Results

All 10 exposed individuals developed an acute illness clinically compatible with trichinellosis, characterized by fever, abdominal pain, and diarrhea, along with eosinophilia ranging from 0.9 × 109/L to 6.1 × 109/L. Within 2 weeks of the diarrheal illness, systemic symptoms developed in all exposed individuals characterized by fever, myalgia, periorbital edema, and fatigue. ST-elevation myocardial infarction and sinus venous tract thrombosis occurred as a complication of trichinellosis in 2 patients. Acute serology was nonreactive in all patients, though convalescent serology was reactive in 6 of 8 (75%) patients for whom sera was available. Multiplex PCR identified T. nativa from the bear meat, and was corroborated by microscopic larval identification.

Conclusions

We report a 100% attack rate of T. nativa from bear meat among those who were exposed, and demonstrate that this species can cause serious thrombotic complications of trichinellosis in humans. Education of hunters and the public regarding the importance of proper preparation of wild game prior to ingestion is warranted.